植物分析與施肥(5)利用葉片分析檢定本省主要茶區NPK需要狀況

Abstract

The purpose of this paper is in an attempt to find out the precision ways in diagnosis of tea manuring with the aid of plant analysis in connection with soil tests. Field trials of six treatments (N0PK, N40PK, N80PK, N120PK, N80K, and N80P) arranged in a randomized block system with six replications have been simultaneously laid out in the following four groves, i.e., Lin-ko, Taipei; Pinchon, Taoyuan; O-mei, Hsinchu; and San-wan, Miaoli, since 1960. To minimize the errors derived from the soil variance and the heterogenity of individual plant before the experiment started, a blank test, namely, each plot received the same rate of nitrogen, say 40 kg/ha N, was conducted in the first year. From second year on, the plots were treated as mentioned above. The second young leaves from the terminal of a new tender shoot having one bud and three young leaves on it were taken for plant analysis from various treated plots in the summer season annually. In the summer of 1966, soil samples were also separately taken at various depths (0~20, 20~40, and 40~60 cm) from the plots treated with N0PK, N80K, N80P, and N80PKsince 1961. After air dried, the soil samples were analyzed for available P by the BRAY'S method (0.025N HCL-0.03N NH4F) and available K by neutral ammonium acetate method. The results of this experiment may be summerized as follows: 1. Data obtained form the experiments indicted the necessity of a blank test before field trial started, because the data obtained from the blank test cant be used for calculating the soil variance within each field trial and for calibrating the results obtained from the formal trial, when the regression coefficient between them was significant. 2. It was found that the yield of tea leaves was greatly affected by fertilizer treatments, years, and their interactions. 3. In general, the increase in the yield of tea leaves was in accompany with the increasing rate of nitrogen applied in the four groves tested. The significant responses of tea to phosphatic and potash fertilization was found in San-wan, Miaoli, and Pinchen, Taoyuan, respectively. 4. The application of N usually increased the leaf-N concentration but lowered the leaf-K concentration. Only in the grove of Pinchen, the leaf-K concentration derived from the plots without potash added was lower than those with potash. Leaf-P concentrations were not greatly affected by fertilizer treatments in each grove with the exception of San-wan where the leaf-P concentration in the plots treated without P was less than those in the plots with P. 5. The relationships of leaf-N concentration to the annual yield of tea leaves were significant. The nitrogen critical concentration and optimum N-level of tea leaves for different groves were the same, namely, less than 4.0% N and 4.25% ~4.75% N, respectively. The significant correlation between leaf-P concentration and the yierd of tea leaves was found in San-wan, Miaoli, where the response of tea to phosphatic fertilization appeared at leaf phosphorus level lower than 0.26% P. Significant relationship of leaf-K to the yield of tea leaves was also found in Pinchen, Taoyuan where the plant was suffered from potash starvation, when the leaf-K concentration was lowered than 1.0% K. 6. From the results of analyzing available PK content of soil samples, they indicated that available PK content were generally decreased with the deptht of soils. Generally speaking, the soil from San-wan contained the least available P and from Pinchen, the least available K in comparison with those form other groves. It is interested to note that the correlation coefficient between the percentage yield of tea leaves (NK/NPK×100) and soil P was increased with the depth of soil and significant relationship between them was found at the depth of 40~60 cm below the surface soil. The some tendency was also appeared in soil K. It, thus, leads to the fact that soil sample from the plot raised with deep-rooted crop for diagnosis should be taken at the right depth. In addition, they indicated that the responses of tea to PK fertilization was obtained when the content of available P and K in the different depths of soil fell below to 3~2 ppm and 45~30 ppm K, respectively.